There seems to be a venting issue with my new Outlander. If I run for any length of time at high rpms the engine will start to sputter and the gas line bubble is sucked flat. Seems to get worse as gas tank empties (from about half full down). The problem is remedied by opening up the gas fill cap and re-pumping the bubble, but I shouldn't have to do this. I pulled up the deck and checked all the lines and everything seems in proper working order. Any suggestions, short of taking it back to the dealer?